Sex chromosome distribution in human gametes

Steps:

• Females have two X chromosomes (XX), so meiosis produces eggs each with one X.
• Males have one X and one Y (XY), so meiosis produces sperm with either X or Y.
• All eggs thus carry an X chromosome, determining female offspring if fertilized by Y-sperm.
• Only half of sperm carry Y, the rest carry X, leading to 50/50 sex ratio.

Why A is correct:

• Egg cells are produced by XX females, so by definition, each egg inherits one X chromosome via meiosis.

Why the others are wrong:

• B: Sperm from XY males carry either X or Y, not exclusively Y.
• C: Eggs from XX females carry X, not Y.
• D: Sperm from XY males carry either X or Y, not exclusively X.

Final answer: A